Field of the Invention
The present invention relates to a novel optically active compound useful as a chiral dopant, a liquid crystal composition containing the compound, and a liquid crystal display device to which the liquid crystal composition is applied. More specifically, it relates to a chiral dopant having a helical twisting power (to be called xe2x80x9cHTPxe2x80x9d for short) of at least 50 and a use thereof.
Various modes are known as display modes of liquid crystal display devices, and in most of such display modes, it is required to control the helical pitch of a liquid crystal. The mode that requires the control of the helical pitch of a liquid crystal includes the following modes. The modes that have been practically and widely used are a twisted nematic mode (TN mode) and a super twisted nematic mode (STN mode) both using a nematic liquid crystal.
In the TN mode, liquid crystal molecules are aligned so as to twist 90 degrees between an upper substrate and a lower substrate, and a xc2xc pitch of a helix is formed in a cell.
In the STN mode, liquid crystal molecules are aligned so as to twist approximately 220 degrees between an upper substrate and a lower substrate, and an approximately ⅗ pitch of a helix is formed in a cell.
The TN mode is employed in a simple matrix driving liquid crystal display device and an active matrix driving liquid crystal display device, and the STN mode is employed in a simple matrix driving liquid crystal display device.